One of the general objectives of this research program is to relate the genetic control of serum proteins, especially immunoglobulins, to their chemical structure, biosynthesis and biological function. As a first step, antibody reagents are prepared which identify the allotypic antigenic determinants of the protein and then the genetic control of these determinants of the protein and then the genetic control of these determinants are delineated with respect to allelism and linkage. The primary goals for the coming year are: 1) to characterize further that sub-unit of IgA which bears the f and g locus allotypic specificities and to evaluate the biological function of colostral IgA, 2) to characterize the a, b, or c locus negative molecules in allotype- suppressed rabbits and to assess the relationship of genetic heterogeneity to molecular heterogeneity, 3) to characterize the active component of the RNA extracts and to evaluate the mechanism of its activity by utilizing a cell culture system for radioactive leucine incorporation into the foreign immunoglobulins along with the use of various metabolic inhibitors, 4) to study the kinetics of synthesis of foreign allotype by RNA extracts, 6) to pin-point the peptides in immunoglobulins which have allotypically related amino acids, 7) to develop lymphocyte lines in rabbit which produce different allotypes in vitro, 8) to investigate immunoglobulin allotype synthesis in vitro and factors which alter gene function in vitro.